The present invention relates to an electronic tone generating apparatus and signal-processing-characteristic adjusting method for use with the apparatus which can impart an acoustic feel, sounding effects peculiar to a natural musical instrument, etc. to tones to be generated, utilizing acoustic conditions of the interior of a room or other space in which the electronic tone generating apparatus is installed.
The acoustic feedback system has been known which performs tone control, such as extension of reverberation, on the basis of existing indoor acoustic conditions in an electric acoustic manner, and principles of such an acoustic feedback system are illustratively shown in FIG. 1. In the acoustic feedback system of FIG. 1, a speaker 12 and microphone 14 are installed an appropriate distance from each other in the interior of a room 10, a tone picked up by the microphone 14 is supplied, as a picked-up tone signal, to an FIR (Finite Impulse Response) filter 18 via a head amplifier 16, to thereby generate a reverberation signal (primarily, initial reflected sound signal). Then, the generated reverberation signal is output via an amplifier 20 to the speaker 12, so that the amplified reverberation signal is audibly reproduced by the speaker 12 and the thus audibly-reproduced tone is again picked up by the microphone 14. By repeating such a sequence of the tone processing, the acoustic feedback system permits increase in a tone volume feeling (i.e., increase in a tone pressure level), increase in a reverberation feeling (i.e., extension of a reverberation time), increase in an expansion feeling (i.e., increase in sideways reflected sound energy), etc. Thus, with the acoustic feedback system, it is possible to crease a sound field feeling as if tones were being performed in a large hall or other large space, although the room 10 is small in fact.
Sound field control apparatus employing the above-mentioned acoustic feedback principles perform processing to adjust frequency characteristics of picked-up tone signals generated by the microphone 14 picking up tones, in order to secure stability against undesired howling. Contents of the frequency characteristic correction process, to be performed on the picked-up tone signals generated by the microphone 14, would differ depending on installed conditions of the microphone 14 and speaker 12. Thus, where the sound field control apparatus used is of a type designed to perform only predetermined contents of the frequency characteristic correction process, it can not carry out appropriate signal processing if there has occurred a change in the installed conditions of the sound field control apparatus, which would invite inconveniences such as howling. Even in the case where the sound field control apparatus used is of a type capable of varying the frequency characteristic correction process as required, it is necessary for the user to adjust, after installation of the control apparatus, the contents of the frequency characteristic correction process through manual operation in accordance with the installed conditions of the apparatus.
In view of the foregoing, it is an object of the present invention to provide an electronic tone generating apparatus and signal-processing-characteristic adjusting method for use with the apparatus which can impart an acoustic feeling etc. to a tone to be generated using acoustic conditions in the space of an existing room, and which can also automatically prevent inconveniences, such as howling, even when an installation environment etc. of the apparatus have changed.
In order to accomplish the above-mentioned object, the present invention provides an electronic tone generating apparatus comprising an electronic tone generator for generating tone signals of a first channel and second channel, and a first speaker and second speaker for audibly reproducing tones corresponding to the tone signals of the first channel and second channel, respectively, generated by the electronic tone generator. The electronic tone generating apparatus further comprises: a first microphone provided at a position corresponding to the first speaker; a second microphone provided at a position corresponding to the second speaker; a first signal processing section that performs predetermined signal processing on a picked-up sound signal generated by the first microphone picking up a sound and thereby outputs a processed picked-up sound signal; a second signal processing section that performs predetermines signal processing on a picked-up sound signal generated by the second microphone picking up a picked-up sound and thereby outputs a processed picked-up sound signal; a third speaker, provided at a position corresponding to the first speaker, for audibly reproducing a sound corresponding to the processed picked-up sound signal output by the first signal processing section; a fourth speaker, provided at a position corresponding to the second speaker, for audibly reproducing a sound corresponding to the processed picked-up sound signal output by the second signal processing section; and a setting section that, when an instruction for setting contents of signal processing is given, supplies a measuring sound signal to the third speaker and fourth speaker, and sets contents of the signal processing to be performed by the first signal processing section on the basis of a picked-up sound signal generated by the first microphone during a predetermined measuring period when sounds corresponding to the measuring sound signal are being audibly reproduced by the third speaker and fourth speaker, and contents of the signal processing to be performed by the second signal processing section on the basis of a picked-up sound signal generated by the second microphone during the predetermined measuring period.
In the electronic tone generating apparatus thus arranged, as tones corresponding to tone signals of two channels are audibly reproduced, i.e. as stereo reproduction of the two-channel tone signals (including monaural reproduction of a same tone signal through two channels) is performed, the audibly-reproduced tones are picked up by the first and second microphones to generate picked-up tone signals, then the picked-up tone signals of the first and second microphones are processed by the first and second signal processing sections, respectively, and then the resultant processed picked-up tone signals output from the first and second signal processing sections are audibly reproduced via the third and fourth speakers, respectively. Namely, if each of the first and second signal processing sections performs a reverberation impartment process etc., there can be achieved reverberation impartment etc. utilizing acoustic characteristics of an installation environment, such as the shape of a space, in which the tone generating apparatus of the invention is installed; namely, there can be achieved the so-called xe2x80x9cacoustic feedbackxe2x80x9d. Thus, the present invention can faithfully reproduce sounding effects peculiar to a natural musical instrument, reverberation produceable in a space surrounding a performing stage, etc. Generally, in the case where the acoustic feedback is utilized, it is necessary to adjust contents of processing to be performed by the first and second signal processing sections, in accordance with the installation environment of the apparatus. However, the tone generating apparatus of the invention is arranged to automatically adjust the contents of the processing by means of the setting section once an instruction for adjusting the contents is given. Here, the contents adjustment is performed on the basis of measured results of stereophonically-reproduced two-channel measuring sounds, namely, the contents of the processing to be performed by each of the signal processing sections are adjusted on the basis of the measured result including signal components of the other channel, with the result that the adjustment can be performed taking into account acoustic inconveniences likely to be caused by from crosstalk and the like.
The present invention also provides an electronic tone generating apparatus comprising an electronic tone generator for generating a tone signal, and a main speaker for audibly reproducing a tone corresponding to the tone signal generated by the electronic tone generator. The electronic tone generating apparatus further comprises: a microphone provided at a position corresponding to the main speaker; a signal processing section that performs predetermined signal processing on a picked-up sound signal generated by the microphone and thereby outputs a processed picked-up sound signal, the signal processing section including a first equalizer, FIR filter and second equalizer; an auxiliary speaker for audibly reproducing a tone corresponding to the processed picked-up sound signal output by the signal processing section; and a setting section that, when an instruction for setting contents of signal processing is given, sets contents of the signal processing to be performed by the signal processing section. The setting section performs adjustment processing in an open loop condition where the signal processing section is interrupted at a given interrupting point thereof and during a time period in which the auxiliary speaker is being caused to audibly reproduce a sound by receiving a measuring sound signal input via the interrupting point. The adjustment processing in the open loop condition measures a frequency characteristic of a picked-up sound signal generated by the microphone and fed back to the interrupting point of the signal processing section, then corrects the measured frequency characteristic on the basis of a picked-up signal generated by the microphone while audible sound reproduction by the main speaker and auxiliary speaker is stopped, and then adjusts a characteristic of the first equalizer of the signal processing section so that a measured frequency characteristic of a sound signal after correction of the measured frequency characteristic by the setting section becomes a flat characteristic. The setting section also performs adjustment processing in a closed loop condition where a signal passage loop of the signal processing section is closed and during a time period in which the auxiliary speaker is being caused to audibly reproduce a sound by receiving the measuring sound signal input via the interrupting point. The adjustment processing in the closed loop condition measures a frequency characteristic of a picked-up sound signal generated by the microphone, then corrects the measured frequency characteristic on the basis of a picked-up signal generated by the microphone while audible sound reproduction by the main speaker and auxiliary speaker is stopped, and then adjusts a characteristic of the second equalizer of the signal processing section so that a frequency characteristic of a picked-up sound signal generated by the microphone after correction of the measured frequency characteristic by the setting section becomes a flat characteristic.
In the electronic tone generating apparatus thus arranged, as tones corresponding to tone signals are audibly reproduced, each of the audibly-reproduced tones is picked up by the microphone to generate a picked-up tone signal, then the picked-up tone signal is processed by the signal processing section, and then the thus-processed picked-up tone signal is audibly reproduced via the auxiliary speaker. Namely, if the signal processing section performs a reverberation impartment process etc., there can be achieved reverberation impartment etc. (in other words, xe2x80x9cacoustic feedbackxe2x80x9d) utilizing acoustic characteristics of an installation environment, such as the shape of a space, in which the tone generating apparatus of the invention is installed. Thus, the present invention can faithfully reproduce sounding effects peculiar to a natural musical instrument and reverberation produceable in a space surrounding a performing stage. Generally, in the case where the acoustic feedback is utilized, it is necessary to adjust contents of processing to be performed by the signal processing section, in accordance with the installation environment of the apparatus. However, the tone generating apparatus of the invention is arranged to automatically adjust the contents of the processing by means of the setting section once an instruction for adjusting the contents is given. Here, the contents adjustment is performed on the basis of measured results of a measuring sound actually reproduced. Because the present invention corrects the measured results on the basis of measured results obtained when the apparatus was not generating a tone at all (i.e., on the basis of measured results of background noise) and then uses the thus-corrected measured results in the contents adjustment processing, it can perform the adjustment processing with an increased accuracy.
According to another aspect of the present invention, there is provided a method for adjusting signal processing characteristics of a first signal processing section and second signal processing section included in an electronic tone generating apparatus which comprises: an electronic tone generator for generating tone signals of a first channel and second channel; a first speaker and second speaker for audibly reproducing tones corresponding to the tone signals of the first channel and second channel, respectively, generated by the electronic tone generator, a first microphone provided at a position corresponding to the first speaker; a second microphone provided at a position corresponding to the second speaker; the first signal processing section that performs predetermined signal processing on a picked-up sound signal generated by the first microphone picking up a sound and thereby outputs a processed picked-up sound signal; the second signal processing section that performs predetermined signal processing on a picked-up sound signal generated by the second microphone picking up a sound and thereby outputs a processed picked-up sound signal; a third speaker provided at a position corresponding to the first speaker, the third speaker audibly reproducing a sound corresponding to the processed picked-up sound signal output by the first signal processing section; and a fourth speaker provided at a position corresponding to the second speaker, the fourth speaker audibly reproducing a sound corresponding to the processed picked-up sound signal output by the second signal processing section. The method of the invention comprises: a step of, when an instruction for setting contents of signal processing is given, supplying a measuring sound signal to the third speaker and fourth speaker, and a step of setting contents of the signal processing to be performed by the first signal processing section on the basis of a picked-up sound signal generated by the first microphone during a predetermined measuring period when sounds corresponding to the measuring sound signal are being audibly reproduced by the third speaker and fourth speaker, and contents of the signal processing to be performed by the second signal processing section on the basis of a picked-up sound signal generated by the second microphone during the predetermined measuring period.
The present invention also provides a method for adjusting a signal processing characteristic of a signal processing section included in an electronic tone generating apparatus which comprises: an electronic tone generator for generating a tone signal; a main speaker for audibly reproducing a tone corresponding to the tone signal generated by the electronic tone generator; a microphone provided at a position corresponding to the main speaker; the signal processing section that performs predetermined signal processing on a picked-up sound signal generated by the microphone and thereby outputs a processed picked-up sound signal, the signal processing section including a first equalizer, FIR filter and second equalizer; and an auxiliary speaker for audibly reproducing a sound corresponding to the processed picked-up sound signal output by the signal processing section. The method of the invention comprises: a step of, when an instruction for setting contents of signal processing is given, performing a) adjustment processing in an open loop condition where the signal processing section is interrupted at a given interrupting point thereof and during a time period in which the auxiliary speaker is being caused to audibly reproduce a sound by receiving a measuring sound signal input via the interrupting point, the adjustment processing in the open loop condition measuring a frequency characteristic of a picked-up sound signal generated by the microphone and fed back to the interrupting point of the signal processing section, then correcting the measured frequency characteristic on the basis of a picked-up signal generated by the microphone while audible sound reproduction by the main speaker and auxiliary speaker is stopped, and then adjusting a characteristic of the first equalizer of the signal processing section so that a measured frequency characteristic of a sound signal after correction of the measured frequency characteristic by the setting section becomes a flat characteristic, and b) adjustment processing in a closed loop condition where a signal passage loop of the signal processing section is closed and during a time period in which the auxiliary speaker is being caused to audibly reproduce a sound by receiving the measuring sound signal input via the interrupting point, the adjustment processing in the closed loop condition measuring a frequency characteristic of a picked-up sound signal generated by the microphone, then correcting the measured frequency characteristic on the basis of a picked-up signal generated by the microphone while audible sound reproduction by the main speaker and auxiliary speaker is stopped, and then adjusting a characteristic of the second equalizer of the signal processing section so that a frequency characteristic of a picked-up sound signal generated by the microphone after correction of the measured frequency characteristic by the setting section becomes a flat characteristic.
The following will describe embodiments of the present invention, but it should be appreciated that the present invention is not limited to the described embodiments and various modifications of the invention are possible without departing from the basic principles of the invention. The scope of the present invention is therefore to be determined solely by the appended claims.